1. Field of the Invention
The present invention generally relates to a Wireless Local Area Network (WLAN), and more particularly to an apparatus and method for estimating available throughput in the WLAN.
2. Description of the Related Art
Extensive research is being conducted to provide users with services based on various Qualities of Service (QoS) at a transmission rate of about 100 Mbps, in the fourth-generation (4G) communication systems serving as next-generation communication systems. In the current 4G-communication system, research is actively being conducted to support a high-speed service for ensuring mobility and QoS in Broadband Wireless Access (BWA) communication systems such as Wireless Local Area Network (WLAN) and Metropolitan Area Network (MAN) communication systems.
With the development of communication systems, one of the more flexible data communication systems implemented in an extension or alternative plan of an existing wired LAN is the WLAN. The WLAN employs a wireless medium for transferring data, which is different from the wired LAN employing a wired medium in the existing wired LAN. Using the wireless medium, the WLAN provides a service previously provided by the wired LAN.
FIG. 1 illustrates a conventional wireless communication network.
Referring to FIG. 1, the wireless communication network includes fixed nodes, i.e., Access Points (APs) 110 and 160, and mobile nodes, i.e., terminals 111, 113, and 161, for receiving services from the APs 110 and 160.
The APs 110 and 160 perform a function similar to that of a hub of the existing wired LAN. AP#1 110 has a service area 100 for communicating with a plurality of terminals including terminals 111 and 113. AP#2 150 has a service area 160 for communicating with a plurality of terminals including terminal 161.
Terminal#1 111 receives a service from the AP#1 110. It is assumed that the terminal 113 can receive a service through AP#2 160 as well as AP#1 110.
When network resources for receiving the current service are insufficient or the terminal 113 moves, a resource reservation or handover operation for the terminal 113 may be required. In this case, the terminal 113 estimates available resources of the AP 110 and the neighbor AP 160. The terminal 113 estimates available throughput of the AP.
Two methods are conventionally used to estimate the available throughput of an AP. In the first method, the AP acquires traffic information to be transmitted to each terminal and estimates its throughput. In the first method, the AP broadcasts information about the estimated throughput to its service area in a regular period. When the first method is used, the AP is to collect the traffic information. Because the AP processes data, the AP load increases. There is a problem in that a bandwidth waste occurs since the information about the estimated throughput needs to be periodically broadcast.
In the second method, a terminal estimates throughput of an AP before performing a call setup process relative to the AP. In the method for estimating the throughput in the terminal, a Network Allocation Vector (NAV) is used. The terminal estimates the throughput of the AP from a packet. However, there is a problem in that the throughput cannot be correctly estimated when a packet collision occurs.
To address the above-described problems, a method is needed which can correctly estimate available throughput of an AP in an existing WLAN without degrading system performance.